Issue during the "Build-essential" installation
 

I have just now installed Ubuntu Fiesty but when I am trying to run the command:

aptitude install linux-headers-`uname -r` build-essential


It says :
Reading package lists... Done
Building dependency tree
Reading state information... Done
Reading extended state information
Initializing package states... Done
Building tag database... Done
Couldn't find any package whose name or description matched "build-essential"
No packages will be installed, upgraded, or removed.
0 packages upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 0B of archives. After unpacking 0B will be used.
Writing extended state information... Done

My source-list file contains:
---------------
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.

deb cdrom:[Ubuntu-Server 7.04 _Feisty Fawn_ - Release i386 (20070415)]/ feisty main restricted
deb http://in.archive.ubuntu.com/ubuntu/ feisty main restricted
deb-src http://in.archive.ubuntu.com/ubuntu/ feisty main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://in.archive.ubuntu.com/ubuntu/ feisty-updates main restricted
deb-src http://in.archive.ubuntu.com/ubuntu/ feisty-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## universe WILL NOT receive any review or updates from the Ubuntu security
## team.
deb http://in.archive.ubuntu.com/ubuntu/ feisty universe
deb-src http://in.archive.ubuntu.com/ubuntu/ feisty universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://in.archive.ubuntu.com/ubuntu/ feisty multiverse
deb-src http://in.archive.ubuntu.com/ubuntu/ feisty multiverse

## Uncomment the following two lines to add software from the 'backports'
## repository.
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://in.archive.ubuntu.com/ubuntu/ feisty-backports main restricted universe multiverse
deb-src http://in.archive.ubuntu.com/ubuntu/ feisty-backports main restricted universe multiverse

deb http://security.ubuntu.com/ubuntu feisty-security main restricted
deb-src http://security.ubuntu.com/ubuntu feisty-security main restricted
deb http://security.ubuntu.com/ubuntu feisty-security universe
deb-src http://security.ubuntu.com/ubuntu feisty-security universe
deb http://security.ubuntu.com/ubuntu feisty-security multiverse
-------------------------------------------------------------------

Plzz help???

Uncomment (i.e. put a # in front of) the "deb cdrom" line and run sudo aptitude update before trying to install.